Many micromachined absolute pressure sensors function by mounting the material removal side of the silicon sense die into glass. Such a methodology can create an absolute pressure sensor. In general, an absolute pressure sensor can employ a sealed volume of gas or vacuum on one side of a diaphragm, with another side of the diaphragm being exposed to a sensed fluid.
An example of a conventional absolute pressure sensor is disclosed in International Patent Publication No. WO 03/064989 A1 to Gregory D. Parker, which published under the Patent Cooperation Treaty (PCT) on Aug. 7, 2003, and is entitled, “An Absolute Micromachined Silicon Pressure Sensor with Backside Hermetic Cover and Method of Making the Same”. International Patent Publication No. WO 03/064989 A1 is incorporated herein by reference and generally describes an absolute micromachined pressure sensory geometry that provides resistive or piezoresistive strain gauges, conductive traces, wire bond pads, and other electrical components on a micromachined silicon die.
The problem with such conventional geometric absolute pressure sensor arrangements and relationships is that the wire bond pads and active regions of the sense die end up facing the sensed media. Exhaust gas contains acids and other chemicals that can penetrate protective gels over time and attack the sense die and its wire bonds. Additionally, conventional absolute pressure sensor configurations lack the ability to process pressure and temperature signals from more than one absolute sense die.
A need therefore exists for improved pressure sensor systems and methods in which pressure and temperature sensing signals are converted into the digital realm and calibration functions are implemented to achieve the desired absolute and differential pressure values, followed by conversion back to analog to provide a final output.